1. Field of the Invention
This invention broadly relates to close-coupled submersible electric pumps and more particularly relates to a bearing bracket assembly for such pumps.
2. Description of the Prior Art
There are many applications wherein mechanical seals are used about rotating shafts that pass through nonrotating walls for the purpose of sealing one side of the wall from the other. Such a situation is most commonly found in pumps where the pumped medium in the pump housing must be prevented from passing into the housing of the driving unit.
In order to decrease the risk of leakage, two mechanical seals are usually arranged between the pump housing and the driving unit housing. It is common to provide a space between the two mechanical seals and to fill this space with oil for the purpose of cooling and lubricating the sealing surfaces. It is also possible to ascertain the condition of the seals by examining the oil. In order to facilitate the replacement of seals, they are usually mounted in a single mounting bracket so that they may be removed as a unit. An example of such a device is shown in U.S. Pat. No. 2,950,931.
Heretofore, the prior art seal assemblies have suffered from several disadvantages. The pair of mechanical seals and the intermediate oil space were axially disposed and therefore encompassed a considerable length of the motor shaft. Thus, the drive shaft between the motor and the pump impeller was excessively long having a tendency to bend and increased bearing loads caused by the cantilever effect. Thus, the shaft had to be quite thick in order to keep shaft bending within reasonable limits and larger size bearings were required to handle the increased bearing load. The additional shaft length severely reduced the heat transfer from the bearings and the motor to the pump housing where the heat was dissipated into the pumped medium. The seals were also quite sensitive to axial expansion of the drive shaft.